Floating lift for watercraft with inflatable pontoons

ABSTRACT

A floating low profile watercraft lifting apparatus comprises a buoyant support apparatus and a watercraft lift attached to the buoyant support apparatus. Embodiments of the lift have first and second cantilever arms pivotally mounted to a base at offset pivot points for use in shallow water. The lift includes an actuator connected to the first and second cantilever arms and operable to move the first and second cantilever arms between a collapsed configuration and an extended configuration with uniform application of force and a minimum amount of travel of actuator components. The support apparatus comprises inflatable pontoons within a frame attached to the lift and providing buoyant support for the lifting apparatus.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No. 10/816,992, filed Apr. 2, 2004, which is a continuation of PCT Application No. PCT/US01/46253, filed Oct. 23, 2001, which is a continuation-in-part of U.S. application Ser. No. 09/316,928, filed May 21, 1999, and claims priority from U.S. provisional application No. 60/086,428, filed May 22, 1998, entitled LOW PROFILE LIFT FOR WATERCRAFT.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to lifting devices, specifically to improvements in such devices that are employed to lift watercraft, for example boats and seaplanes.

2. Description of the Related Art

Users of watercraft have need to lift their watercraft from the water, for example for maintenance or in preparation for land transportation of the watercraft. Equally, watercraft users have need to lower their watercraft into the water, for example for launching or simply for flotation at dock. Users have heretofore employed a number of devices for such lifting and lowering.

Exemplary of such devices is U.S. Pat. No. 5,184,914, issued to the inventor of the present invention which is incorporated herein by reference and discloses a watercraft lifting device having a rectangular stationary base formed of two longitudinal parallel beams and two transverse beams, generally described as front and rear transverse, beams. The rectangular base is submersible under water. Pivoting booms connect each of the four corners of the rectangular base to swingable mounting arms positioned parallel to and coplanar with each of the longitudinal beams to form two pairs of pivoting booms, generally described as front and rear pivoting booms. The two pair of pivoting booms form with the mounting arms collapsing parallelograms on which watercraft supports extended a predetermined distance above the mounting arms hold the craft during lifting. A double-acting hydraulic cylinder is pivotally connected to the rear transverse beam and its piston rod is pivotally connected to the two front pivoting booms such that expansion of the double-acting cylinder extends the piston rod and swings front pair of pivoting booms upward from a collapsed configuration. The parallelogram linkage forces the mounting arms and rear pair of pivoting booms to follow the front pair of pivoting booms. Thus, expansion of the double-acting hydraulic cylinder raises the front pair of pivoting booms and lifts the rear pair of pivoting booms, the mounting arms and the watercraft supports attached to the mounting arms upward to lift a watercraft out of the water. Upward movement continues until the pivoting booms pass through a vertical orientation into an over-center orientation whereby the watercraft is supported above the surface of the water.

Retraction of the piston rod into the piston jacket of the double-acting hydraulic cylinder reverses the motion of the pivoting booms. Thus, retraction of the double-acting hydraulic cylinder first raises the pivoting booms and lifts the mounting arms and watercraft supports attached to the mounting arms upward. Upward movement causes the pivoting booms to pass back through vertical orientation. Continued retraction of the piston rod into the double-acting hydraulic cylinder combined with the weight of the latching apparatus and the watercraft collapses the parallelograms whereby the watercraft is lowered into the water. The piston rod continues to retract into the double-acting hydraulic cylinder collapsing the parallelograms, including the mounting arms and watercraft supports attached to the mounting arms, until contact between the watercraft supports and the watercraft is broken and the watercraft can float free.

Although the apparatus of the prior art operates effectively in many practical applications, a need exists for a floating watercraft lifting apparatus that operates effectively in shallow water applications where the typical water depth is minimal and the apparatus of the prior art cannot collapse sufficiently to break contact between the watercraft supports and the watercraft and release the watercraft to float free, and where the depth of the water varies due to tides, seasonal fluctuations, and the like. Such an apparatus is specified and claimed in currently pending U.S. application Ser. No. 10/816,992 by the inventor of the present invention, incorporated herein by reference.

The invention claimed in application '992 comprises a boyant support apparatus and a watercraft lift attached to the boyant support apparatus. Embodiments of the boyant support apparatus disclosed in '992 are rigid pontoons, preferably comprised of sectional airtight flotation chambers having a hollow interior. While floating watercraft lifts are advantageous generally for reasons set forth above, rigid pontoons for such an apparatus present several limitations.

First, the required dimensions for boat lift pontoons presents significant manufacturing costs if rigid pontoons are employed. A floating boat lift, such as the Floatlift™ model FL 6012 from Sunstream Corporation must have pontoons providing roughly 8,300 pounds of buoyancy, requiring displacing roughly 1000 gallons of water. Even if boat lift pontoons are manufactured sectionally, as described in application number '992, manufacturing rigid pontoons of such large displacement entails considerable difficulty and cost. Second, shipment of such large rigid pontoons to the site where the boat lift is to be assembled and deployed entails additional difficulty and cost. Third, disassembly of a floating lift, whether for maintenance or relocation, is more complicated when large rigid pontoons are involved.

What is needed is a floating boat lift that offers the advantages of such lifts generally but that does not have the disadvantages associated with large rigid pontoons.

BRIEF DESCRIPTION OF THE INVENTION

The present invention improves upon prior art floating watercraft lifts by providing a buoyant support apparatus comprised of inflatable pontoons. The pontoons comprise inflatable tubular chambers, typically fabricated of polymer coated fabric sheet material. The inflatable buoyant support apparatus attaches to the watercraft lift via rigid attachment means. Advantageously, the pontoons may be shipped deflated to the boat lift location and, in situ, both inflated for deployment and deflated for maintenance or relocation.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing objects, as well as further objects, advantages, features and characteristics of the present invention, in addition to methods of operation, function of related elements of structure, and the combination of parts and economies of manufacture, will become apparent upon consideration of the following description and claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures, and wherein:

FIG. 1 is a perspective view of a floating watercraft lift in the raised, over-center position, according to the present invention.

FIG. 2 is a front elevational view of a floating watercraft lift in the raised position, according to the present invention.

FIG. 3 is a side elevational view of a pontoon affixed to support apparatus according to the present invention.

FIG. 4 is a detail of a pontoon affixed to support apparatus in a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1 and FIG. 2, floating lift 100 comprises a watercraft lift apparatus 102 affixed to a buoyant support frame 104. In the depicted embodiment, the support frame 104 includes two adjustable transverse beams 106, 108 that are attached to lift 102 by connectors 110 located on each end 112 of parallel longitudinal beams 114 a, 114 b on lift 102. Attachment to connectors 110 may be accomplished by welding, fasteners, or other known methods. Transverse beams 106, 108 are formed of tubular metal having a substantially square cross-sectional shape that defines a hollow longitudinal interior 116 that opens at each end 118. Lift 102 holds transverse beams 106, 108 in spaced parallel relationship.

In use, the floating lift 100 is positioned in a body of water with the support frame 104 attached to the floor of the body of water. The support frame stands upon support stands 120, resting upon base plates 122, suitably secured in a conventional manner that will not be described in detail herein. Stands 120 connect to catwalks 124 via arcuate bands 126, which encompass inflatable pontoons 128. Pontoons 128 may be inflated with air or other gas to provide buoyancy. In the depicted embodiment, catwalks 124 rest upon floating inflatable pontoons 128 and thereby support buoyant support frame 104. While the preferred embodiment is depicted, other arrangements for the inflatable pontoons 128 to provide buoyancy to frame 104 are within the scope of the present invention. For example, both the catwalks 124 and the pontoons 128 may be directly connected to frame 104.

In this embodiment, stands 120 are laterally positioned by sliding the lateral beams 130 with respect to front and rear transverse beams 106, 108 and affixing them with suitable fasteners. Once base plates 122 are anchored, buoyant support frame 104 is adjusted vertically along adjustment post 129, thus keeping lift 102 at the right height with respect to the surface of the water.

As depicted, pontoons 128 are each comprised of pairs of tubes of polymer coated fabric material, made airtight and fitted with valves for inflation and deflation in the manner of inflatable rafts of rubberized fabric, well known to those in the art. As will be appreciated by those of skill in the art, a wide variety of other configurations of inflatable pontoons are possible in keeping with the teachings of the present invention. It is preferred that each pontoon 128 comprise a plurality of inflatable members, so that in the event of a rupture, the pontoon will still retain partial buoyancy.

As will be further appreciated by those of skill in the art, other embodiments of the present invention are possible wherein inflatable pontoons are fabricated of materials other than polymer coated fabric, such as sheet elastomer or heavy gauge sheet mylar®. It is to be understood that pontoons comprised of any material are within the scope of the present invention, so long as such pontoons may be inflated with air for flotation and are substantially reduced in volume when deflated.

In the presently depicted embodiment, pontoons 128 are secured to catwalks 124 by nautical ropes 130 which are threaded through handles 132 that are affixed to pontoons 128. The depicted handles 132 are comprised of a rigid material, such as solid polymer, affixed to pontoon 128 by bonding to a rigid or semi-rigid reinforcing sole within pontoon 128, and made airtight with pontoon 128 by polymeric seal with the material comprising pontoon 114, in a manner well-known to those in the art. As will be appreciated by those of skill in the art, various other conventional means may be employed to secure inflatable pontoons 128 to catwalks 124. By way of example, such means may include nylon straps instead of nautical ropes. By way of further example, pontoon 128 may be secured to catwalk 124 by a connecting means such as a clamp attached to catwalk 124 which directly engages an attachment such as handles 132 in the pontoon 128. By way of yet further example, catwalk 124 may be integral to pontoon 128, comprising a rigid or semi-rigid element disposed within and/or bonded to the polymer coated fabric or other material comprising pontoon 128.

Watercraft lift apparatus 102 may be of any design whose dimensions and extensions in operation are accommodated by buoyant support frame 104. An exemplary lift apparatus is that described in U.S. Pat. No. 5,184,914, issued to the inventor of the present invention and incorporated herein by reference. In the depicted embodiment, lift 102 comprises a base made up of front and rear beams 134, 136 and transverse beams 114 a, 114 b. Two pair of upwardly extending booms 138, 140 are each pivotally connected at their lower end to the base at its corners. The members of each pair of booms are rigidly connected to each other in parallel by cross supports 142, 144. Two substantially horizontal arms 146 are each pivotally connected to one member of each pair of booms 138, 140 at the upper end of the boom, so that each arm pivotally connects to one member of one pair of booms 138 at one end of the arm and to one member of the other pair of booms 140 at the other end of the arm. Two connected, collapsible parallelograms are thereby formed, one on each side of the base formed by 114 a, 114 b, 134 and 136, the corners of each parallelogram comprising the upper and lower pivot points of the front and rear booms 138, 140 on one side of the base. The pivotally connected arms lie in a plane, which is lowered as the parallelograms are collapsed and is raised when the parallelograms are expanded. A watercraft supported by support means connected to the arms in that plane may thereby be lowered and raised as the parallelograms are respectively collapsed and expanded. An expanding and contracting actuator, 146, such as a hydraulic cylinder, supplies the motive force for expanding the parallelogram for lifting watercraft.

In preferred embodiments of watercraft lifts, such as claimed in '914, the parallelogram expands over-center, so that initially obtuse angles of the parallelogram become acute and initially acute angles become obtuse, providing an advantageous, gravity-based locking for raised lifts. Such a lift requires that the actuator be double-acting, providing expanding actuation for raising, but also providing contracting actuation for moving the lift back over center for lowering, as provided preferably by a double-acting hydraulic cylinder. As will be appreciated by those of skill in the art, however, the present invention will accommodate a wide range of embodiments of watercraft lift 102, not limited to those expressly described herein.

CONCLUSIONS, RAMIFICATIONS, AND SCOPE

Accordingly, it can be seen that the invention described herein provides an improved floating watercraft lift apparatus wherein the buoyancy of the lift is supplied by inflatable pontoons. Because the pontoons are inflatable and deflatable, the pontoons may be shipped deflated to the boat lift location and, in situ, both inflated for deployment and deflated for maintenance or relocation.

Although the detailed descriptions above contain many specifics, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Various other embodiments and ramifications are possible within its scope, a number of which are discussed in general terms above.

While the invention has been described with a certain degree of particularity, it should be recognized that elements thereof may be altered by persons skilled in the art without departing from the spirit and scope of the invention. Accordingly, the present invention is not intended to be limited to the specific forms set forth herein, but on the contrary, it is intended to cover such alternatives, modifications and equivalents as can be reasonably included within the scope of the invention. The invention is limited only by the following claims and their equivalents. 

1. A floating watercraft lift, comprising: a buoyant support apparatus having a support frame configured to be anchored with respect to a body of water and a floatable frame mounted on the support frame, the floatable frame comprising inflatable pontoons, and a watercraft lift apparatus supported by the buoyant support apparatus.
 2. A floating watercraft lift according to claim 1, wherein said lift apparatus comprises: a base; a first pair of booms having a first pair of ends pivotally joined to said base to rotate about a first axis and a boom extension projecting from said first pair of ends thereof; a second pair of booms having a first pair of ends pivotally joined to said base to rotate about a second axis; watercraft supports pivotally connected to said pairs of booms; an actuator pivotally connected to at least one of said first and second pair of booms, said actuator operable for forcing said pivoting booms from a lowered position to a raised position relative to said base to raise said watercraft supports, and said actuator operable for retracting said pivoting booms from the raised position to the lowered position to lower said watercraft supports.
 3. A floating watercraft lift according to claim 1, wherein said buoyant support apparatus further comprises a catwalk
 4. A floating watercraft lift according to claim 1, wherein said floatable frame is slideably mounted on the support frame.
 5. A floating watercraft lift according to claim 2, wherein said actuator is double-acting and said lift apparatus expands over-center to provide gravity-locking functionality in the raised position. 